ScienceDaily has an item on research by S. Lourenco on the concept of magnitude in babies (here). It is published in Psychological Scinece, General Magnitude Representation in Human Infants.

“We’ve shown that 9-month-olds are sensitive to ‘more than’ or ‘less than’ relations across the number, size and duration of objects. And what’s really remarkable is they only need experience with one of these quantitative concepts in order to guess what the other quantities should look like,” Lourenco says… “Babies like to stare when they see something new,” Lourenco explains, “and we can measure the length of time that they look at these things to understand how they process information.”

When the infants were shown images of larger objects that were black with stripes and smaller objects that were white with dots, they then expected the same color-pattern mapping for more-and-less comparisons of number and duration. For instance, if the more numerous objects were white with dots, the babies would stare at the image longer than if the objects were black with stripes.

“When the babies look longer, that suggests that they are surprised by the violation of congruency,” Lourenco says. “They appear to expect these different dimensions to correlate in the world.”

The findings suggest that humans may be born with a generalized system of magnitude. “If we are not born with this system, it appears that it develops very quickly,” Lourenco says. “Either way, I think it’s amazing how we use quantity information to make sense of the world.”

From an good developmental program point of view: what we are born with we do not have to take time or effort to build and do not have to risk mistakes; but, what we are not born with can be learnt in a flexible, plastic way that will fit our environment but this takes time, effort and may fail to be ‘right’. A compromise is to be born with a few very important things in-born with all else being build within the framework of the in-born framework. So we are probably born with a bare model of the world – 3 dimensional space, the passage of time, space populated by objects, and so on. Magnitude is a useful idea to be born with, only learning to apply it - rather than having to first understand aspects of the world in order to create the idea of magnitude. This framework will be a constant feature of conscious experience.